In the mid-late-1980s, half the world's email went through 'ihnp4' (google
it) via UUCP. That was a cluster of machines running SVRx.
When you're the phone company, calls are free. :) This is the best article I saw:
www.nobell.org/~gjm/about/ihnp4.html Let's also remember seismo and decvax which had phone bills in the tens of thousands per month. And they weren't free.
I was the moderator of mod.sources, everyone wanted to call me. mirror!rs :)